Vol. 5, No. 2 / February 2018 / Optica 159

All-electronic terahertz nanoscopy

Vol. 5, No. 2 / February 2018 / Optica 159 (2018)

Probing conductivity in a contactless way with nanoscale resolution is a pressing demand in such active fields as
quantum materials, superconductivity, and molecular electronics. Here, we demonstrate a laser- and cryogen-free
microwave-technology-based scattering-type scanning near-field optical microscope powered by an easily aligned
free-space beam with a tunable frequency up to 0.75 THz. It uses Schottky diode components to record background-free
amplitude and phase nano-images, for the first time in the terahertz range, which is uniquely sensitive
for assessing conduction phenomena. Images of Si with doped nanostructures prove a conductance sensitivity corresponding
to 1016 cm−3 mobile carriers, at 50 nm spatial resolution.